Manufacturing process for piston engines having compression ring sealing

ABSTRACT

Manufacture of engines having grooved pistons and sealing rings fitting in the grooves of the pistons comprising: selection, by means of a selection-rejection process from a plurality of torsion type split compression rings, of rings for the grooved pistons each having at least the first one of its two opposite sides, in the free spring state of the ring, provided with a consistent overall flatness to at least about 10 to 5 light bands and, in the collapsed state with the ring closed or substantially so, said first side being frusto conical and so arranged with respect to the back of the ring that the intersecting portion of the inner periphery of the first side is substantially coplanar at all points on the periphery; sealing said pistons with such compression rings including those rings as so selected, by installation of a ring in an associated compression ring groove on each piston with an associated side of the groove confronting in the described way the first side of the ring; and construction of said engines by assembling such pistons in the respective cylinders with the face of each ring engaging a cylinder wall at all times to retain the ring in collapsed state on the piston, and with the ring effective during engine operation to establish a substantially continuous pressure ring of at least line contact between the coplanar inner periphery of said frusto conical first side and its associated confronting groove side to seal the piston.

United States "Patent [91 Packard [4 1 Aug. 14, 1973 MANUFACTURINGPROCESS FOR PISTON Primary Examiner-Richard J. Herbst ENGINES HAVINGCOMPRESSION RING Assistant EXaminer--V. A. DiPalma SEALINGAttorney-Floyd B. Harman [75] Inventor: Norman M. Packard, Des Plaines,Ill.

10 IRA T [73] Ass1gnee: International Harvester Company, [57] A s CChicago, Ill. Manufacture of engines having grooved pistons and sealingrings fitting in the grooves of the pistons com- [22] F'led: June 1971prising: selection, by means of a selection-rejection [211 App]. No.:156,558 process from a plurality of torsion type split compressionrings, of rings for the grooved pistons each having Related ApplicationData at least the first one of its two opposite sides, in the freeDivision Of 1- 6, 1968. Pat. spring state of the ring, provided with aconsistent overall flatness to at least about 10 to 5 light bands and,in the collapsed state with the ring closed or substantially US. Cl-

R, R, so side fmsto conical and so arranged 29/222, 29/428, 51/290,51/324, 277/216 with respect to the back of the ring that theintersecting [5 In. portion of the inner of the first side sub- [58]Field of Search 29/l56.4 R, 156.5 R, Stamiany coplanar at all points onthe periphery; Seal- 29/156.6, 156.63, 407, 222; 73/1 19, 120; ing saidpistons with such compression rings including 277/ 103; 51/290 324 thoserings as so selected, by installation of a ring in an associatedcompression ring groove on each piston with References Cited anassociated side of the groove confronting in the de- UNITED STATESPATENTS scribed way the first side of the ring; and construction1,572,801 2/1926 Kearney..l 29/222 of Said engines y assembling SuchPistons in the l,593,220 7/1926 Phelps 29/222 spective cylinders withthe face of each ring engaging 2,177,700 10/ l 939 Fisher 277/216 acylinder wall at all times to retain the ring in collapsed 2,697,87012/1954 Zucker 29/222 state on the piston, and with the ring effectiveduring 2 engine operation to establish a substantially continuous T3886pressure ring of at least line contact between the coplalgOZZl nar innerperiphery o aid f usto conical first side and its associated confrontinggroove side to seal the piston.

5 Claims, 11 Drawing Figures PATENIED Ann 1 4 ma sum 2 or 2MANUFACTURING PROCESS FOR PISTON ENGINES HAVING COMPRESSION RING SEALINGThis application is a division of the same assignees Packard applicationSer. No. 757,973 filed Sept. 6, 1968, now US. Pat. No. 3,587,155.

Blowby presents a problem in production piston engines. The need, as Ienvision it, is to control blowby so that in production we are capableboth of making it predictable and of keeping it at a uniform, desirablylow value from engine to engine, at least in precision made productionengines which, in general, are of the multi-cylinder type. Blowby is oneof the factors affecting lubricating oil control. Solving the blowbyproblem will have a material influence on reducing oil consumption inengines, and I have discovered that the key to the solution is in thecompression rings on the pistons.

According to my inventions, the engines are sealed, i.e., each pistonand its surrounding cylinder wall are mutually sealed by an interposedpiston ring either so selected that the inner peripheral edge of thering at the groove sealing side thereof is coplanar at all points orelse so localizedly lapped, in a narrow band along the inner peripheraledge at the side, that the ring will seal the confronting side of areceiving groove in a narrow, circumferentially continuous ring ofpressure contact which amounts to line contact or, at most, has onlyslight width at the widest points. The resulting ring at the side of thepiston ring makes up only a minor portion of the overall side. Theoverall side of the ring which seals the groove side as aforesaid forms,for at least its major portion as viewed in cross section, a slightangle to the groove side and is frusto conical although the groove sidemay or may not be frusto conical.

The disparity in the angularity between the mutually confronting sealedand sealing sides of the respective receiving groove and piston ring isdeliberate, and under pressure during compression and firing in theengine cylinder the ring deflects into what amounts to face contact withthe groove side over at least a major portion of the side of the ring,thus multiplying to substantial proportions the sealing area at thecritical time. So sealing with narrow band contact and line contact orsealing with face contact, depending upon the presence or absence ofhigh pressure conditions, complement one another to reduce the blowby,i.e., escape of firing pressure into the crankcase by leakage in thecylinders past the pistons.

My inventions thus materially reduce or substantially eliminate theproblem of unpredictability and largely uncontrollably high magnitude ofblowby, as will now be explained in detail.

Features, objects, and advantages will either be specifically printedout or become apparent when, for a better understanding of theinventions, reference is made to the following description taken inconjunction with the accompanying drawings which show certain preferredembodiments thereof and in which:

FIG. 1 is a longitudinal elevational view of a portion of a piston andcylinder in an engine embodying the present ringinvention, and shownwith the embodiment in one of its operating positions in collapsedstate;

FIG. 2 is an enlarged fragmentary view corresponding to FIG. I, butshowing that embodiment of the invention in another operating position;

FIG. 3 shows the embodiment of FIG. I in the same collapsed state, butin a lapping fixture for doing the work on the ring to bring it to thefinished stage;

FIGS. 4, 5, and 6 are sequence views of the ring as lapped, showing therespective beginning, intermediate, and finished stages;

FIG. 7 corresponds to FIG. 2, insofar as a fully seated or firingposition is being viewed, but showing a modified piston and ringstructure;

FIGS. 8 and 9 are similar to FIGS. 1 and 2, insofar as respective lineseated and fully seated positions are being viewed, but showing afurther modified piston and ring structure;

FIG. 10 corresponds to FIG. 8, but with the ring in a lapping fixture tobring it to the final stage; and

FIG. 11 corresponds to FIG. I, insofar as a line seating position isbeing viewed, but showing a further modification of the ring.

My inventions about to be particularly described apply to, among others,rectangular positive torsion ring structure, keystone rings with eitherplain structure or positive torsion structure, and rectangular negativetorsion or reverse dish ring structure. Slightly oversimplified, apositive torsion ring is basically one which is twisted in a ring grooveof rectangular cross section with the lower side of the ring bearingagainst the bottom of the groove at the radially inner part of thegroove and inclining upwardly and outwardly therefrom. A positivetorsion keystone ring is, to a much more moderate extent, along the samelines above but it fits in a tapered or wedge shaped groove on a piston.A keystone ring without torsion causing it to twist in the groove is aplain keystone ring, but it nevertheless fits in a wedge shaped groove.Finally, the negative torsion ring twists in a rectangular groovewhereby what the ring does is to have the upper side of the ring bearagainst the top of the ring groove in the inner part of the groove,slanting downwardly and outwardly therefrom, or else what the ring doesis to have the lower side of the ring bear against the bottom of thering groove in the outer part of the groove, inclining upwardly andinwardly therefrom, or else the ring does both.

All of the rings concerned are the so-called split rings, having aparting located at some point around the circular length of the ring.Each such ring is compressed from its normal relaxed or free state bymeans of a ring compressor so that it assumes a collapsed state with theparting closed or substantially so. In reaching the collapsed state, thetorsion ring twists or distorts or dishes out of its normal plane inwell known way dependent upon whether the curved inner face at the backof the ring has been selectively undercut at one side or the other ofthe ring. When collapsing, the torsion ring always takes a dishedposition with the undercut portion ocupying what becomes the concaveside of the dish.

The metal of the foregoing rings is usually cast iron, and the pistonsare cast iron or an aluminum alloy. Pistons in the latter category havethe compression ring grooves formed either directly in the aluminum orin hardened, grooved inserts carried by the aluminum piston.

Against this background, it is believed that FIGS. I, 2, 3, 4, 5, and 6,showing one preferred embodiment of my ring invention, can be readilyunderstood.

LINE SEATED OPERATION. COLLAPSED STATEFIG. 1

A rectangular, positive torsion ring is shown in that one of itsoperating positions in an engine in which the ring is line seated at theside, i.e., a narrow seal band 22 thereon establishes at least linecontact with the inner portion of the confronting lower side 24 of arectangular groove 26 in a piston 28. The piston reciprocates within thewall 30 of a cylinder of a multicylinder engine 32, being sealed to thewall by the ring 20. The ring 20 is a compression ring, and isillustrated in the top or first ring position on the piston although thedesign is fully effective as the second, third, etc., compression ringon a multi-ringed piston.

The adjacent ends of the ring defining the parting indicated at 34 arepractically touching at the operating temperature of the ring, but ineach engine the designer always takes care to keep them from actuallybottoming against one another because of the danger that the ring mightseize in the cylinder. The ring is thus a live ring, functioning at alltimes as a cast iron spring.

In the collapsed operating state in the groove as shown in FIG. 1 thering has a twisted position, due to its inherent torsion, during thesuccessive exhaust and suction strokes of the piston 26. The slightacute face angle, which the essentially cylindrical face 36 of the ringmakes with the vertical, accounts for a unidirectional oil pumpingaction produced by the ring. During the exhaust strokes referred to eachof which is in the outward (upward) direction, the ring provides goodoil control, keeping an oil film on the hone pattern in the wall 30 at asufficient but minimum thickness for lubrication purposes. During eachsuction stroke, which is inward, the ring 20 due to its slight faceangle scrapes the oil in the inward (downward) direction because of theclosed pocket formed by the contact between the ring and each of thecylinder wall 30 and the lower groove side 24. The oil cannot readilyget into the groove 26 because of the ring of pressure contact of thesealing band 22, and so the oil is pushed inwardly ahead of the bottomside of the ring indicated at 38 and now to be described in connectionwith the operating conditions of compression and firing.

FULLY SEATED OPERATION. COLLAPSED STATEFIG. 2

During the successive compression and firing strokes of the piston 28,the ring of pressure contact effected by the line-seated seal band 22always insures as a first stage of sealing that no appreciable pressuredissipation can take place by leakage past the ring. Hence, the ring 20is flattened by the ensuing build-up of pressure and, by a second stageof sealing, the bottom side 38 of the ring is forced into a fully seatedarea of face contact against the major portion of the confronting bottomside 24 of the groove 26.

The trapped pressure produces a consequent downward and outward forceagainst the respective flat upper side 40 and curved rear side 42 at theback of the ring. Hence, the curved face 36 at its lower edge is bothspring loaded mechanically and pressure loaded by gas into essentiallyleak-free contact with the cylinder wall 30.

Although not present to the exaggerated extent as shown in FIG. 2, thereis in fact an obtuse angle of intersection between the band 22 and themajor portion of the lower side 38. The respective lower and upper sides38 and 40 are parallel, horizontal, and flat both in this face contactcollapsed state for obvious reasons and in the state now to bedescribed.

NORMAL RELAXED OR FREE STATE-FIG. 3

In the free spring state of the ring having a fully expanded diameter asshown by the broken lines 20a in FIG. 3, the adjacent ends of the ringmove to their fully withdrawn position so that they are partedconsiderably at 34. It is when the spring is unloaded and in free state,during the manufacturing process, that the respective upper and lowersides 40 and 38 are made flat and parallel, and the side 38 ispreferably lapped in a lapping fixture to within the range of 10 to 5light bands or to greater flatness, such as to two light bands flat atstandard inspection wavelength (helium). Hence, the bottom side 38 ofthe ring will provide effective face sealing when in the fully seatedoperating position shown in FIG. 2.

In order to make the ring 20 twist because of its cross section, thecurved rear side or back 42 is relieved by an undercut adjacent the topside 40 only, as by a chamfer or, as actually illustrated, a counterbore44. So there is definite asymmetry in the cross section whereby, whenthe parting in the ring is closed, the ring dishes into an upwardlyconcave collapsed form, now to be further discussed.

LAPPING, BEGINNING STAGE-FIG. 3

An aspect of novelty is believed to reside in the fact that, prior to mydiscovery of the realities of the matter, there had been and never wasany basis for accepting as a foregone conclusion that a positive torsionring, flat on the bottom side in free state, would so uniformly distortinto its collapsed state as to establish line contact with a groove sidewhich was to be sealed thereby and which was planar or substantially so.Prior to my discovery, and consistently confirmed as a fact in randomchecks made by me, it was never appreciated and yet as a general rulethe usual production-made positivetorsion ring in collapsed state wasnon-coplanar along its sealing inner periphery which presented asuccession of high spots and low spots, somewhat according to a wavy orundulating pattern. Hence, there existed no fundamentally orderly andsystematic way whereby the engine designer or assembler could predictthe amount of blowby which would be produced by each engine when finallybuilt.

One of my methods of providing a piston ring in production engineseffective to control the blowby and oil consumption to an exceptionalproportion by better sealing includes, as a first step, compressing aring, such as the ring 20 in FIG. 3, radialwise into its collapsed statein the movable fixture 46 of a lapping apparatus. The ring receivingmouth 48 of the fixture has identical diameter to the cylinder bore sizeof the engine in which the ring 20 is to be installed. The lappingapparatus further includes a flat, fixed confronting lapping surface 50,the ring 20 being held relative thereto so that the side 38 forms at alltimes a slight acute angle to the flat surface 50. The mouth 48 of thefixture 46 is, on the one hand, shallow enough that the inner peripheryonly of the lower side 38 of the ring projects into contact with thesurface 50. At the same time, the shallow mouth 48 is nevertheless deepenough to engage the outer periphery of the side 38, where the latterjoins with the face 36 of thering, thereby retaining the ring in acollapsed state the same as if restrained in operating condition in acylinder of the nominal bore size of the engine. 7

In the case of the usual positive torsion piston ring prior to mydiscovery, low spots would be present on the inner periphery at the sideof the ring 20 which would not contact the surface 50 at the beginningof lapping.

LAPPING, INTERMEDIATE STAGE-FIG. 5

Lapping is preferably accomplished by forced motion of the fixture 46 ina figure eight movement in the plane of the fixture and ring relative tothe fixed surface 50. Other specific movements to produce equivalentlapping can be utilized, the critical factor being to preventperpendicularly loading the fixture 46 on the surface 50. About onepound total perpendicular pressure has been found acceptable, withoutproducing the undesirable result of distorting the ring 20 from thenormal twisted position into which it would be distorted by torsion whenoperating in a compression ring groove in an engine.

The first points abraded by the lapping compound on the flat surface 50will be the high spots 52 initially forming circumferentially spacedapart flats on the inner periphery of the lower ring side 38. Continuedabrading by the surface 50 keeps lowering the high spots 52 relative tothe plane of the lowest spots of the inner periphery.

LAPPING, FINISHED STAGE-FIG. 6

In the'stage illustrated in FIG. 6, the lapping of the ring 20 hasprogressed to the final stage, all lapping having been performed withthe parting 34 closed or substantially so although the parting isgreatly emphasized in the figures of drawing to illustrate presence ofthe gap. All spots will have merged into the common continuous sealingband 22 with the former high spots forming the widest portions 52a inthe band. Here again, the band width is greatly exaggerated to beperceptible in the illustration. Because of its finite width dimension,the band 22 can be literally said to have flatness, and such flatness ismeasurable and preferably in a range equivalent to at least about to 5light bands at standard inspection wavelength (helium). No greaterapproach has been found necessary to perfect flatness of the seal bandin order to achieve the practical control of blowby desired, although 2light bands would, for example, improve the operation at leasttheoretically.

Anyway, the precise range of flatness is not the matter of basicimportance here involved, but rather it is systematic analysis andinsurance in all cases of a good sealing contact. So a band of theflatness and specific shape of the varied width band 22 as shown in FIG.6 is not necessarily the most desirable, nor is the provision of a banddesirable in all cases.

BAND CONTACT. NARROW WIDTH Achieving sealing contact by what is believeda better way than the foregoing is by the provision of a ring having aband of essentially uniform narrow width, not illustrated.

Since my discovery, it has been observed that at times .positive torsionrings produced in manufacture include somerings which, by happenstance,have a protruding inner periphery which in the collapsed state of thering is practically coplanar at all points. Despite their randomoccurrence, the marshalling out of such rings by a selection-rejectionprocess is feasible, and each of those rings in such a select group islapped only slightly whereupon the group will have fully advanced to thefinished stage. Inherently, such rings have a very narrow sealing band,almost uniform in width, and they highly successfully seal in accordancewith the principles of my inventions.

LINE CONTACT-FIG. 6

Perhaps the best way, and no doubt the ideal way, of accomplishing thesealing hereof is to apply the selection-rejection process and separateout all rings in a production run which by happenstance display precisecoplanarity of the inner periphery at all points when the ring isdistorted into the collapsed state.

In fact since my discovery, it has been observed that careful control inring manufacture over such variables as metallurgy, manufacturingprocedure, and details of ring design such as cross section and thelike, can materially increase the proportion of rings in a productionrun above what could be expected as the happenstance or random grouphaving coplanarity of the inner periphery of the bottom side at allpoints. So through careful control of the manufacturing process andother variables, the deliberate increasing of the proportions of suchrings in a run can be realized to an expectancy of 50 percent andbetter, perhaps upwards of 90, or percent, or possibly of 98 percent,which will have what can be stated as the coplanarity inherency in theperipheral portion of the ring when distorted into collapsed state.Stated another way, the inner periphery of the sealing side of the ringin each case is a uniplanar knife edge.

In such case, the product becomes not the happenstance or exception butthe rule, and what essentially amounts to absolute line contact ofsealing, i.e., contact having only a substantially continuous lengthdimension and no width, can be achieved with the ring. To tell thetruth, the confronting side of the groove which is sealed by such a ringin service actually acts as a lapping surface to a degree, and in thecourse of engine operation the groove side can lap the ring peripheryfrom an edge into a band.

Obviously, the selection-rejection process will have to be retained atleast to the extent of a spot check Though possible, it sounds somewhatidealistic to expect to achieve rings which to a 100 percent extent haveinner peripheries on each of which the locus of all points will fall inone plane. Practical manufacturing does not allow absolutepredictability and certainly the manufacture of positive torsion ringswhich must be distorted to install them does not allow absolutepredictability. 4

The ring of FIG. 45 can be viewed as such a ring having substantiallyabsolute coplanarity along the inner periphery, and it will beunderstood that the parting at 341 although greatly exagerratedcorresponds to the operative parting or split or gap in the ring incollapsed state in the line seated position. The spot checking, referredto, of such production rings is no destructive test, and a ring sotested is merely lapped a few test strokes to the point where theresulting uninterrupted flat band can be perceived visually. The ring isperfectly usable, establishing in the line seated position a FULLYSEATED, POSITIVE TORSION KEYSTONE RING-FIG. 7

In the modification of FIG. 7, the parts are the same except that a ring60 as shown is a positive torsion keystone ring and the receiving groove62 therefor is a complementary wedge shaped groove having a taper.Similarly to the preceding embodiment, the back of the ring 60 isundercut at 64 with a counterbore in the upper part of the curved innerside of the ring. The ring 60 has a bottom side 66 provided with alapped seal band 68 located at the inner periphery where the bottom sidejoins with the back of the ring.

The ring 60 is not shown in its line seated operating position whichoccurs in the collapsed state and which can be readily visualized.Instead, FIG. 7 shows the ring in its fully seated position in collapsedstate providing a wide area of face sealing contact with the confrontingbottom side 70 of the receiving groove 62.

Consistent with the usual design of keystone rings, the ring 60 has abarrel face 72 which as viewed in cross section affords a smoothcurvature making contact with a confronting cylinder wall 74 as the ring60 changes between'line seated and fully seated positions in the groove.

The operation is the same as in the preceding embodiment, during boththe consecutive exhaust and intake strokes of the engine on the one hand(line seated), and the consecutive compression and firing strokes of theengine on the other hand (fully seated).

In customary manner, the bottom side 66 of the ring 60 in collapsedstate in the line seated position (not shown) makes a slight angle tothe horizontal, whereas the groove side 70 is machined with a slightangle to the horizontal which is nevertheless somewhat larger than thereferred to angle of the ring side 66. Hence, the ring 60 reacts inoperation by fully seating against the groove side 70 under compressionand firing pressures in the engine.

Most torsion type rings are of rectangular shape, which rings usuallyhave the greater susceptibility to ring sticking because of the shape.Inasmuch as keystone rings are substantially free from susceptibility tosticking, most of the keystone rings are plain keystone rings.

KEYSTONE RING, PLAIN-FIGS. 8 and 9 A plain keystone ring is illustratedat 80 in collapsed state in the respective line seated position in FIG.8 and fully seated position in FIG. 9. During exhaust and intakestrokes, essentially line contact according to the inventive principleshereof is effected between a flat seal band 82 forming the innerperiphery of the bottom side 84 of the ring and a confronting bottomside 86 of the wedge shaped or tapered ring receiving groove 88. Duringcollapse of the ring 80 from its free spring condition, not shown, tothe collapsed, line seated, operating position as shown in FIG. 8, nottwist occurs because no twist-providing asymmetry is present in thecross section of the ring 80. Only line contact results because thegroove side 86 is machined to have a slight angle to thehorizontal'which is somewhat greater than the slight angle which thering side 84 makes with the horizontal.

Both the compression pressure and the firing pressure in the enginecause the ring side 84 to fully seat in face contact against the bottomside 86 of the groove, as shown in FIG. 9.

PLAIN KEYSTONE, LAPPING-FIG. 10

For purposes of lapping the keystone ring is, with no attendant twistbecause of lack of torsion from asymmetry, collapsed from the freespring state indicated by the broken lines 80a to the line contactposition in collapsed state as shown by the solid lines 80 in FIG. 10. Alapping fixture 92 therefor has an open mouth 94 holding the ring incollapsed state with the inside and outside diameters of the respectivemouth and ring equal to the cylinder bore size of the engine for whichthe ring is designed. The inner periphery only of the bottom side 84projects into contact with a fixed confronting lapping surface 96.

The lapping surface 96 is convex, being for example, frusto conical or,as actually illustrated, frusto spherical. The ring 80 is maintained ina consistent attitude relative to the surface 96 so as to have thebottom side 84 form the same slight angle thereto at all times. Figureeight lapping movement or other suitable motion of the fixture 92relative to the fixed lapping surface 96 abrades away the high spots andshapes the inner periphery of the side 84 into a seal band 82 which canlie along a groove side in a continuous line.

The shallow mouth 94 is shallow enough not to interfere with the surface96 and yet is at the same time deep enough to insure that the ring 80 isfirmly retained in collapsed state.

The groove for the keystone ring is, in contrast to the grooves for theother n'ngs herein described, never narrow enough so that the ringsimultaneously touches the upper and lower grooves sides. Hence, thekeystone ring when within a comparatively wide groove, as well as theother rings when within similarly appropriately wide receiving grooves,are forced into the line seated operating position against the bottomside of the groove only on the exhaust stroke. Nevertheless the lineseated position offers help which is of a critical nature duringcompression and firing, but offers no help at all during suction when,in point of fact, the ring is drawn up against the upper side of thegroove. During compression and firing as just referred to, the lineseated position is critical for sealing at the first stage in orderthat, as the second stage, the rising pressure can accumulate and causefull seating of the ring in face contact with the lower side of thegroove.

In torsion rings, simultaneous engagement between the ring and bothsides of the groove (i.e., the groove is comparatively narrow in thesense just referred 'to) is, desirable when the amount of ring twist isto be limited by engagement of the ring with both sides of the groove.Simultaneous engagement is also desirable for other reasons and, if notessential, is especially desirable with certain rings. For example, somenegative torsion rings can display a deficiency both during exhaust andalso during compression and firing by its failure to establish properline seated position because of the inherent geometric incompatibilitybetween the nonconcentric frusto conical bottom ring side and thecircular outer edge of the groove bottom side.

My inventions aid in overcoming such deficiency in the negative torsionspring embodiment now to be described.

NEGATIVE TORSION OR REVERSE DISH RlNGl1 A negative torsion compressionring 100 is illustrated in FIG. 11. The cross section causes the ring,when collapsing, to twist or distort from its normal relaxed or freespring state into the parting closed state whereby the lower side 102 ofthe ring in contacting the rectangular receiving groove will bearagainst the outer part of the lower groove side 104, inclining upwardlyand inwardly therefrom. The upper side 106 of the ring in simultaneouslycontacting the receiving groove will bear against the inner part of theupper groove side 108, pressing thereagainst with a narrow seal band 112at the ring side periphery and inclining downwardly and outwardlytherefrom.

The negative torsion ring 100, by reason of the undercut 114 thereofbeing located in the back of the ring adjacent the lower side 102,dishes convexly upwardly and serves primarily as a compression ring,preferably as the second, third, etc., compression ring below the firstor top compression ring, not shown.

Notwithstanding the fact that the lower side 102 of the ringtheoretically seals the lower groove side 104 to prevent any oilentering the ring groove, the slight frusto conicity of the side 102 atleast in theory will not firmly seat along the circular confrontingportion of the groove side 104 for the reasons given, except when thetwo are geometrically concentric.

However, the planar band 112 and the confronting planar upper grooveside 108 establish at least line contact in all radially shiftedpositions and therefore prevent passage of oil in or out of the groove.Specifically, close line contact of the band 112 during inward strokesof suction cause line seated sealing. Close line contact of the band 112as the first stage during compression and firing, insuring properpressure rise for the second stage of full seating of the ring, isessential to establishment of the face contact of full seating. Also,line contact of the band 112 which is enforced by the comparativelynarrow rectangular groove during exhaust causes line seated sealing.

The negative torsion ring l'is not illustrated in collapsed state in thefully seated operating position, which can be readily visualized as thestage beyond the point of occupying the position actually illustrated,i.e., the face contact stage beyond the point when the ring 100 is incollapsed state in the line seated operating position illustrated.

The genral utility ofmy inventions as they apply to various ringsisbelieved covered with adequate and representative exampleshereinabove. In the interest of brevity, the specific utility of myinventions is now set out only with respect to the literal line contactmodification of which FIG. 4 is illustrative and the narrow band contactmodification of which FIG. 6 is illustrative, all as embodied in apositive torsion, rectangular ring. The advantage of positive torsion,despite the ring being fitted in a rectangular groove and hence beingsusceptible to sticking, is that the ring has an operatively built-infreedom of twisting motion tending to prevent buildup of carbon inthering groove which, in accumulated quantities therein, can cause ringsticking. The effective sealing accomplished hereby insures twistingunder the periodically trapped pressures, making the rectangularcross-sectional ring to become entirely practicable. The designer canrealize definite cost savings by avoiding turning to a keystone shape,which shape makes for a much more expensive ring due to the inside coneangularity of the maor sides which must be worked upon duringmanufacture of the keystone ring.

There are two sure ways of taking advantage of my inventions to the lastdegree. The way, in the case of the foregoing rings or equivalents whichaccomplish effective line seating not literally so but actually by bandseating, is to accurately lap a narrow seal band on the inner peripheryof the seating side of every ring. The way, in the case of the foregoingrings and equivalents which accomplish line seating substantiallyliterally, i.e., the sealing side of the ring has frusto conicity withthe inner periphery of the side protruding and being substantiallycoplanar at all points on the periphery so as to have practically nowidth dimension, is with enforced selection-rejection by a percentinspection process of all rings whereby any seal ring having aprotruding inner periphery in which all points are not coplanar alongthe periphery is discarded.

At all events, the rings in both cases are used in the same way inengine manufacture, e.g., in the manufacturing process of an engineprovided with a number of cylinders and with that number of ring groovedpistons individual to the respective cylinders. The process comprisessealing the pistons with the compression rings by installation of such aring in each compression ring groove with an associated side of thegroove confronting one sealing side of the ring; and construction ofsuch engines by assembling individual pistons in the respectivecylinders with each ring engaging a cylinder wall at all times to retainthe ring in collapsed state on the piston, and with the ring effectiveduring engine operation such as exhaust or suction to establish asubstantially continuous pressure ring of at least line contact betweenthe protruding inner periphery of the frusto conical one sealing sideand its associated confronting groove side to seal the piston, andduring engine operation such as compression or firing to establish asubstantially continuous pressure ring of full seated contact betweenthe major portion of the frusto conical one side and its associatedconfronting groove side to seal the piston,

Engines so manufactured meet the desiderata of controlled blowby, and ofcontrolled oil consumption to the degree that would be affected byblowby. That is to say, with low blowby being predictable it followsthat oil consumption will be predictably low, in absence of inordinateconditions that might cause the engine to use excessive amounts oflubricating oil.

Broadly, the basic system here involved is to change from the casehitherto of having a good seal between ring side and groove side solelyas the exception or happenstance, and instead to make it the generalrule that the ring side and groove side have a substantially continuousring of pressure contact when the ring is line seated or equivalent(i.e., narrow band seated) and when the ring is fully seated against theside of the groove. Not only is gas leakage avoided in excessive amountssuch as might partially or altogether prevent a torsion ring fromtwisting, but also leakage at the ring is kept within minimum controlledlimits.

As a practical matter, all of the smooth surfaces hereinabove discussedare either substantially flat or substantially cylindrical. Hence, theangularities are admittedly exaggerated in the drawings, particularly inthe case of the face angle of the face 36, FIG. 2 which, in

its practical range of about 1 or 2 or 3 from the vertical would at somepoint be hardly perceptible at all, and also in the case of the bottomside 26, FIG. 1, which is not much greater than the just stated 1 or 2or 3 in angularity from the horizontal.

Variations within the spirit and scope of the inventions described areequally comprehended by the foregoing description.

What is claimed is:

l. A process of manufacturing engines each provided with a number ofcylinders and with that number of ring grooved pistons individual to therespective cylinders, each ring groove having a bottom adaptedconfrontingly to receive the back of a piston ring, and hav' ing thegroove sides confrontingly associated with the respective first andsecond opposite sides of a ring in a manner exposing the face of thering outwardly of the groove, said process comprising the steps of:

selection, by means of a selection-rejection process from a plurality oftorsion type split compression rings, of rings for the grooved pistonseach having at least the first one of said opposite sides, in the freespring state of the ring, provided with a consistent overall flatness toat least about 10 to 5 light bands and, in the collapsed state with thering closed or substantially so, said first side being frusto conicaland so arranged with respect to the back of the ring that theintersecting portion of the inner periphery of the first side issubstantially coplanar at all points on the periphery;

sealing said pistons with such compression rings including those ringsas so selected, by installation of a ring in an associated compressionring groove on each piston with an associated side of the grooveconfronting in the described way said first side of the ring; and

construction of said engines by assembling such pistons in therespective cylinders with the face of each ring engaging a cylinder wallat all times to retain the ring in collapsed state on the piston, andwith the ring effective during engine operation to establish asubstantially continuous pressure ring of at least line contact betweenthe coplanar inner periphery of said frusto conical first side and itsassociated confronting groove side to seal the piston.

2. The invention of claim 1, the inner periphery of said frusto conicalfirst side having all points aforesaid thereof planar to one another toat least the equivalent of about to 5 light bands of flatness.

3. The invention of claim 2, the sealing of the pistons by rings incollapsed state characterized by twisting each ring in the associatedgroove with torsion during engine suction and exhaust so as to rendersaid first side frusto conical, and fully seating each ring in thegroove with pressure during engine compression and firing, causing achange in its sealing position from said continous ring contact to faceseal seating against the side of the groove.

4. A process of manufacturing engines each provided with a number ofcylinders and with that number of pistons individual to the respectivecylinders, said pistons having compression-ring-receiving groovespresenting groove sides associated with respective first and second,opposite ring sides and being flat or substantially so, said rings eachhaving a face, and having a back adapted to be confrontingly received inthe bottom of a groove, said process comprising the steps of:

selection, from a plurality of split compression rings, of rings for thegroove pistons having at least the first one of said opposite sides, forits major portion in the free spring state of the ring, provided with aconsistent overall smoothness and, at least in the collapsed state withthe ring closed or substantially so, said first side being frustoconical and so arranged with respect to the back of the ring that theintersecting portion of the inner periphery of the first side with theback is substantially coplanar at all points on the periphery; sealingsaid pistons with such compression rings including those rings as soselected, by installation of a ring in an associated compression ringgroove on each piston with an associated side of the groove confrontingsaid first side of the ring; and

construction of said engines by assembling such pistons in therespective cylinders with the face of each ring engaging a cylinder wallat all times to retain the ring in collapsed state on the piston, andwith the ring effective during the exhaust strokes of engine operationto establish a substantially continuous pressure ring of at least linecontact between the coplanar inner periphery of said first side and itsassociated confronting groove side to seal the piston, and during thecompression and firing strokes of engine operation to establish asubstantially continuous pressure ring of fully seated contact betweenat least a major portion of said first side and its associatedconfronting groove side to seal the piston.

5. The invention of claim 4, the selection of rings being of ringswhereof the inner periphery fonns a knife edge initially sealing in linecontact; and

operation of said engines whereby the associated confronting side of theassociated compression ring groove laps said knife edge flat in serviceso as to seal in narrow band contact.

1. A process of manufacturing engines each provided with a number ofcylinders and with that number of ring grooved pistons individual to therespective cylinders, each ring groove having a bottom adaptedconfrontingly to receive the back of a piston ring, and having thegroove sides confrontingly associated with the respective first andsecond opposite sides of a ring in a manner exposing the face of thering outwardly of the groove, said process comprising the steps of:selection, by means of a selection-rejection process from a plurality oftorsion type split compression rings, of rings for the grooved pistonseach having at least the first one of said opposite sides, in the freespring state of the ring, provided with a consistent overall flatness toat least about 10 to 5 light bands and, in the collapsed state with thering closed or substantially so, said first side being frusto conicaland so arranged with respect to the back of the ring that theintersecting portion of the inner periphery of the first side issubstantially coplanar at all points on the periphery; sealing saidpistons with such compression rings including those rings as soselected, by installation of a ring in an associated compression ringgroove on each piston with an associated side of the groove confrontingin the described way said first side of the ring; and construction ofsaid engines by assembling such pistons in the respective cylinders withthe face of each ring engaging a cylinder wall at all times to retainthe ring in collapsed state on the piston, and with the ring effectiveduring engine operation to establish a substantially continuous pressurering of at least line contact between the coplanar inner periphery ofsaid frusto conical first side and its associated confronting grooveside to seal the piston.
 2. The invention of claim 1, the innerperiphery of said frusto conical first side having all points aforesaidthereof planar to one another to at least the equivalent of about 10 to5 light bands of flatness.
 3. The invention of claim 2, the sealing ofthe pistons by rings in collapsed state characterized by twisting eachring in the associated groove with torsion during engine suction andexhaust so as to render said first side frusto conical, and fullyseating each ring in the groove with pressure during engine compressionand firing, causing a change in its sealing position from said continousring contact to face seal seating against the side of the groove.
 4. Aprocess of manufacturing engines each provided with a number ofcylinders and with that number of pistons individual to the respectivecylinders, said pistons having compression-ring-receiving groovespresenting groove sides associated with respective first and second,opposite ring sides and being flat or substantially so, said rings eachhaving a face, and having a back adapted to be confrontingly received inthe bottom of a groove, said process comprising the steps of: selection,from a plurality of split compression rings, of rings for the groovepistons having at least the first one of said opposite sides, for itsmajor portion in the free spring state of the ring, provided with aconsistent overall smoothness and, at least in the collapsed state withthe ring closed or substantially so, said first side being frustoconical and so arranged with respect to the back of the ring that theintersecting porTion of the inner periphery of the first side with theback is substantially coplanar at all points on the periphery; sealingsaid pistons with such compression rings including those rings as soselected, by installation of a ring in an associated compression ringgroove on each piston with an associated side of the groove confrontingsaid first side of the ring; and construction of said engines byassembling such pistons in the respective cylinders with the face ofeach ring engaging a cylinder wall at all times to retain the ring incollapsed state on the piston, and with the ring effective during theexhaust strokes of engine operation to establish a substantiallycontinuous pressure ring of at least line contact between the coplanarinner periphery of said first side and its associated confronting grooveside to seal the piston, and during the compression and firing strokesof engine operation to establish a substantially continuous pressurering of fully seated contact between at least a major portion of saidfirst side and its associated confronting groove side to seal thepiston.
 5. The invention of claim 4, the selection of rings being ofrings whereof the inner periphery forms a knife edge initially sealingin line contact; and operation of said engines whereby the associatedconfronting side of the associated compression ring groove laps saidknife edge flat in service so as to seal in narrow band contact.